The present invention relates to a color picture tube having a shadow mask, and in particular, to a structure of the color picture tube, which is designed to alleviate a degradation in image quality which is attributable to oscillations and impacts.
A color picture tube generally comprises a face panel carrying a fluorescent screen, and a shadow mask disposed in opposing relationship with the fluorescent screen and acting as a color selection member. A given positional relationship is maintained between three color phosphors (for example, phosphor stripes), constituting together the fluorescent screen, and openings (or slits) in the shadow mask. Three electron beams emitted from an electron gun are scanned in both horizontal and vertical directions, and can irradiate corresponding color phosphors only when they are allowed to pass through the opening in the shadow mask.
When the above-mentioned color picture tube is subject to oscillations or impacts, the positional relationship between the phosphors and the openings in the shadow mask changes to prevent a proper irradiation of the phosphors by the electron beams as long as the oscillations continue. This presents problems of producing a faint color area in an image being displayed (in other words, displaying uneven color image due to a local reduction in the luminance of an image being displayed) and a color shift as a result of an irradiation by an electron beam of an adjacent phosphor of a different color. A shadow mask of aperture grille type (hereinafter referred to as aperture grille), in particular, is susceptible to oscillations because of its structure in which opposite ends of strips are welded to a frame in order to hold a plurality of strips (i.e., long and narrow piece) taut. Consequently, a color picture tube employing an aperture grille has been liable to a degradation in image quality which is attributable to oscillations and impacts. As one remedy which is intended to suppress oscillations of strips, a pair of damper wires are used in combination with damper springs which support the damper wires. However, for use as a monitor internally housing a loudspeaker or an aircraft onboard color picture tube, the oscillation resistance achieved has been less than satisfactory in certain instances.
It is an object of the present invention to provide a color picture tube which is less susceptible to a degradation in image quality if subjected to oscillations or impacts.
According to one aspect of the present invention, a color picture tube comprises: a face panel which is provided with a fluorescent screen; an electron gun for emitting an electron beam; means for scanning the electron beam in a horizontal and a vertical direction; a shadow mask having a plurality of openings and disposed in opposing relationship with the fluorescent screen; a frame for supporting the shadow mask; and a support member for supporting the frame on the face panel; wherein xcfx89v denotes a vertical scan frequency by the means for scanning, n denotes an arbitrary integer which satisfies 1xe2x89xa6nxe2x89xa66, N denotes an arbitrary integer which satisfies 1xe2x89xa6Nxe2x89xa66, xcfx89 denotes a frequency which satisfies xcfx89=xcfx89v*n/N, xcfx89s denotes a resonant frequency of the shadow mask, and the frame, the support member, and the shadow mask are constructed such that the resonant frequency xcfx89s assumes a value other than the frequency xcfx89.
According to another aspect of the present invention, a color picture tube comprises: a face panel which is provided with a fluorescent screen; an electron gun for emitting an electron beam; means for scanning the electron beam in a horizontal and a vertical direction; a shadow mask having a plurality of openings and disposed in opposing relationship with the fluorescent screen; a frame for supporting the shadow mask; and a support member for supporting the frame on the face panel; wherein xcfx89v denotes a vertical scan frequency by the means for scanning, n denotes an arbitrary integer which satisfies 1xe2x89xa6nxe2x89xa66, N denotes an arbitrary integer which satisfies 1xe2x89xa6Nxe2x89xa66, xcfx89 denotes a frequency which satisfies xcfx89=xcfx89v*n/N, xcfx89s denotes a resonant frequency of the shadow mask, and the frame, the support member and the shadow mask are constructed such that resonant frequency xcfx89s assumes a value other than frequency xcfx89 and rise in a frequency band defined a pair of adjacent frequency values from a series of frequency values xcfx89.
According to a further aspect of the present invention, a color picture tube comprises: a face panel which is provided with a fluorescent screen; an electron gun for emitting an, electron beam; means for scanning the electron beam in a horizontal and a vertical direction; an aperture grille including a plurality of strips disposed in an array and separated from each other by a slit and disposed in opposing relationship with the fluorescent screen; and a frame supported by the face panel for supporting the plurality of strips of the aperture grille at an end thereof; wherein each strip of the aperture grille has a widened part at an end of the strip.